As a capacitor used widely at present, for example, an Al-electrolytic capacitor or a laminated ceramic capacitor has been known. Because the Al-electrolytic capacitor uses an electrolyte solution, it needs countermeasures against liquid leakage and the like. Moreover, because the laminated ceramic capacitor is manufactured through a calcination treatment, it needs to solve various problems caused due to thermal contraction between an electrode and a dielectric.
On the other hand, in recent years, as a new capacitor, a capacitor in which an insulating layer obtained by applying an anodic oxidation treatment to aluminum oxide is used as a dielectric layer is proposed. For example, Japanese Patent No. 4493686 discloses a capacitor including a pair of conductor layers, a dielectric layer, a plurality of minute holes, and first and second internal electrodes, the dielectric layer being provided between the pair of conductor layers, the plurality of minute holes having a substantially columnar shape, the plurality of minute holes being formed so as to penetrate the dielectric layer in a direction substantially perpendicular to the pair of conductive layers, the first and second internal electrodes being filled in the plurality of holes. The first internal electrode is filled in a part of the plurality of holes. One end of the first internal electrode is electrically connected to one of the conductor layers, and the other end of the first internal electrode is insulated from the other conduct layer. The second internal electrode is filled in a hole out of the plurality of holes, which is not filled with the first electrode. One end of the second internal electrode is electrically connected to the other conductor layer, and the other end of the second internal electrode is insulated from the one layer.
The capacitor having such a configuration does not need an electrolyte solution or a calcination treatment. Therefore, it is possible to overcome the problem of the Al-electrolytic capacitor or laminated ceramic capacitor. Moreover, because the first and second internal electrodes to be filled in the dielectric layer have a nanoscale microstructure, the entire element can be downsized. Furthermore, because the first and second internal electrodes are connected to the pair of conductor layers in parallel, it is possible to increase the capacity of an element.